1. Field of the Invention
The present invention generally relates to a test method, and more particularly, to a test method for a storage device.
2. Description of Related Art
Solid-state drives (SSDs) composed of flash memories are becoming increasingly popular in the market. A flash memory is a non-volatile memory that can be electrically programmed and erased. However, the lifetime of a flash memory is limited by of its erase cycles. Thus, when using a SSD composed of flash memories, the reliability of the memory system becomes very important. However, the reliability of a SSD has to be tested by using a client-side test tool.
Presently, there is no any standard method for testing the reliability of a SSD, while the test methods used by different manufacturers can not provide a comprehensive test to the reliability of a SSD. For example, in some existing SSD test methods, the erase bytes/write bytes ratio or the ratio of reduced erase cycles when cache and hot data are accessed is used for indicating the overhead of wear levelling. In some other methods, the reliability of a SSD is determined based on the erase count of the SSD (i.e., by counting the erase cycles of the SSD). Another method is to use an erase count standard deviation and an average value for indicating the overhead of wear levelling, namely, the overall erase count and divergence degree thereof.
In addition, most existing test methods are executed based on an entire storage medium, and accordingly the test report thereof has very low resolution. The test result will be more reliable if the test is performed in unit of blocks. Moreover, in most existing test methods, erase count is the only factor taken into consideration and accordingly errors can be produced in the test result.